The present invention relates to a voice coil of a voice coil motor used in a rotating disk storage device such as a magnetic disk drive or a magneto-optic disk drive, and more particularly to a voice coil which exhibits an excellent performance in a unique shape.
In a magnetic disk drive, a voice coil motor (hereinafter referred to as “VCM”) drives an actuator assembly, causing a head to assume a predetermined position on a magnetic disk. The VCM includes a voice coil mounted on an actuator assembly, a voice coil magnet supported by a base, and a voice coil yoke. To improve the operation performance of the actuator assembly it is important for the voice coil to be light-weight and generate a strong rotating torque and not to generate an unnecessary torque.
FIG. 1 is a perspective view showing a conventional actuator head suspension assembly (hereinafter referred to as “AHSA”) 1 and a voice coil 9 mounted on the AHSA 1. The voice coil 9 is formed by a continuous conductor winding and is held by a coil support 3. As a plane shape in a coil plane of the voice coil 9, such a generally sectorial shape as shown in FIG. 1 has heretofore been adopted traditionally. When coil portions of the sectorial voice coil are represented by coil sides a to d, the coil side b located far from a pivot shaft of the AHSA 1 is longer than the coil side a close to the AHSA 1. The reason is presumed to be as follows. Even when the voice coil 9 approaches a pivoting limit of the AHSA 1, the coil side d and a part of the coil side c (or the coil side c and a part of the coil side d) are prevented from lying within magnetic fields of the same polarity in a yoke gap formed by the voice coil magnet, whereby it is intended to maintain the torque characteristic for a pivotal position as flat as possible. It is also presumed that the coil sides a and b are disposed outside the yoke gap for the purpose of minimizing the force developed by the voice coil 9 and acting in the pivot shaft direction.
Japanese Patent Laid Open No. Hei 10-3761 discloses a voice coil having a unique shape to diminish oscillation in seeking without affecting a driving torque of a carriage generated by a voice coil motor, thereby improving a magnetic head positioning accuracy and eliminating any bad influence on the durability of a magnetic medium to improve the reliability.